The invention relates to a method of monitoring the inclination of a motor vehicle comprising measuring the inclination thereof with an inclination-sensitive sensor, generating variable digital signals by the sensor, evaluating the signals, and triggering an alarm when the signals differ from a reference value.
Methods of protecting motor vehicles which operate on the basis of monitoring the inclination thereof are known. Such methods are intended on the one hand to protect the vehicle itself from being stolen by being loaded on to another vehicle, being pulled up over a ramp, and also on the other hand to prevent the vehicle being lifted by a jack for the purposes of removing and stealing a wheel. In all such operations, the body of the vehicle moves relative to the chassis structure, or the spring components move with respect to other components. Such movements may be shocks, jerky movements or also a lifting movement using a vehicle jack. In all cases, the bodywork of the vehicle changes in inclination with respect to a starting condition. A change in inclination can therefore be used for triggering off an alarm.
However, directly connecting an acoustic and/or optical alarm signal source to a sensor or detector for detecting the inclination of the vehicle would result in a large number of false alarms. It may happen that the vehicle is nudged or bumped against only for a short period of time due to vibration, children playing or the like. The inclination of the vehicle undergoes change. The vehicle returns to a stable position after a period of time of the order of magnitude of perhaps only half a second. It may also happen for example that the vehicle changes its angle of inclination over a longer period of time, under the influence of weather or outside temperature. A coating of snow on the roof of the vehicle may melt off on one side. When the vehicle is parked on a soft piece of ground, it may sink at one side. Likewise, it may happen that the vehicle is caused to oscillate at its natural frequency due to vibration or an impact. They are maintained for a small number of periods and then die away. The vehicle will also oscillate at its natural frequency and, in so doing, change in inclination, when for example children intentionally bounce or rock the vehicle on its suspension. An alarm is not to be triggered off in all such cases. Such an alarm would be a false alarm and would result in the user switching off the alarm installation after a few false alarms had occurred.